In the mining arts it is well known that underground mineral deposits, coal for example, may often be found in seams which slope with respect to the horizontal. Although conventional underground coal mining machinery is commonly used in essentially horizontal coal seams, for example those with a slope less than approximately 4.degree. to 5.degree. with respect to horizontal, such conventional machinery is not well adapted for use in seams with a greater slope, for example a 5.degree. or 6.degree. or greater slope with respect to horizontal.
This is so because conventional mobile underground mining machinery is commonly supported on the mine floor by rubber tires, tracks, or other suitable traction apparatus. The considerable weight of such mining machinery, together with the non-uniformities of the mine floor, and the inherent lubricity of the mine water on the mine floor, all tend to limit the utility of conventional mining machinery on slopes greater than approximately 5.degree. or 6.degree. with respect to horizontal. The machines will tend to slide down-slope in response to the reaction forces of the mining operation, or merely as a result of traction loss during movement of the mobile machine from one site to another in the mine. This diminished mining machine stability on a sloping mine floor is of great concern in view of the limited space and light in an underground coal mine. Obviously, machine instability increases the danger of working around the mining machinery.
Notwithstanding the impracticality of conventional mining machines for use in sloping seams, recovery of coal from sloping seams is contemplated by the prior art. For example, U.S. Pat. No. 4,536,035 discloses a hydraulic mining method which includes drilling a vertical bore hole from the surface into a pitched mineral vein, and a slant bore hole also drilled from the surface along the footwall of the vein to intersect the vertical bore hole. The slant bore hole accommodates a fluid jet stream apparatus to remove material from the mineral vein. The mineral and water mix flows down the slant bore hole into a sump formed by the vertical bore hole and is then pumped up through the vertical bore hole to the surface.
U.S. Pat. No. 4,092,045 discloses a subterranean hydraulic mining system in which a shaft is sunk from the surface into the mineral deposit. A second shaft is drilled from the surface into the same deposit in proximity with the first shaft. Shaped charges are utilized to disintegrate material in the deposit and subsequently water and air are utilized to move the disintegrated material toward the first shaft for recovery of the material by pumping thereof to the surface.
Other patents relating to hydraulic or water jet mining include U.S. Pat. Nos. 4,915,452, 3,797,590, 4,496,191, 4,094,549, 3,993,354 and 3,790,214.